https://leetcode.cn/problems/find-all-numbers-disappeared-in-an-array/


int* findDisappearedNumbers(int* nums, int numsSize, int* returnSize) {
    int arr[numsSize + 1];
    int* tmp = (int*)malloc(numsSize * sizeof(int));
    for (int i = 1;i <= numsSize;i++)
    {
        arr[i] = 0;
    }
    for (int i = 0;i < numsSize;i++)
    {
        if (arr[nums[i]] == 0)
        {
            arr[nums[i]] = 1;
        }
    }
    int count = 0;
    for (int i = 1;i <= numsSize;i++)
    {
        if (arr[i] == 0)
        {
            tmp[count] = i;
            count++;

        }
    }
    *returnSize = count;
    return tmp;
}